131 



For example, at 20 percent spill, 40 percent of the marked fish passed via the spillway at 

 Lower Granite Dam; at 40 percent spill, 60 percent passed via the spillway. Studies at John 

 Day indicated that passage of fish via the spillway was 44 to 56 percent higher than the 

 percentage of water spilled. 



Considering these studies, and that that the mean FGE of the improved bypass 

 systems at Little Goose, Lower Monumental, McNary, and John Day all exceed 69 percent 

 (Lower Granite 75-77%, Lower Monumental 69%, McNamy 80%, and John Day 72%), a 

 much smaller percentage of the water need be spilled than 80% specified by the Biological 

 Opinion to achieve 80% FGE (Kroma et al. (1986), Ledgerwood et al. (1987), Brege £LaL 

 (1992). McComas et al. (1994)). 



The Risk Assessment stotes that 30 to 92 percent of the fish pass through turbines 

 even where screening and bypass systems are installed. This is a very misleading statement. 

 As set forth above, the mean FGE is much higher. At dams where turbines are completely 

 screened (Lower Granite, Little Goose, Lower Monumental, and John Day) guidance ranges 

 from 40 to 80 percent for spring chinook, 75 to 86 percent for steelhead, and 25 to 35 

 percent for subyearlings. Guidance values for Bonneville II are lower, but testing continues 

 there. 



Some of the recent PIT-tag recovery information indicates that the FGE values 

 measured during the studies cited may be too high and the real FGE may be closer to 50% at 

 Little Goose and Lower Monumental Dams. Even accepting these lower FGEs as accurate, 

 given that 40% of the fish will pass at 20% spill, it appears unlikely that TDG of 115% 

 percent in 'the tailrace need be exceeded to achieve 80% FPE. 



This is apparent from an examination of the data concerning specific projects. For 

 example, at Lower Monumental Dam, where the lowest FGE occurs, 15% spill would 

 achieve 80% FGE. Thus, at 100 thousand cubic feet per second (kefs) river fiow, only 15 

 kefs spill would be required. Based on the rating curves for spillway defiectors, this level of 

 spill would probably not exceed 110 percent TDG. 



At Lower Granite Dam, fish guidance efficiency appears to range from 50% early in 

 the season to 80% late the season. Early in the season up to 40 kefs spill may be required to 

 achieve 80% FPE, but if one considers the studies cited earlier, 20% should be more than 

 sufficient. As the season progresses, this spill could be reduced and 80% FPE could still be 

 achieved. 



At Bonneville FGE for spring migrants is about 50%. Again 115% TDG does not 

 need to be exceeded to achieve 80 percent FGE. The only dam where an FPE of 80% 

 percent may not be achieved by maintaining the tailrace concentrations at or below 1 15 

 percent TDG would be Ice Harbor. 



The efficiency of the sluiceway at the Dalles Dam without any screens is near 50 

 percent. Because of the configurations of the dam, small volumes of spill there can pass a 



